Electric-arc lamp.



No. 657,450. Patented Sept. 4, I900.

I L B PRENTISS.

ELECTRIC ABC LAMP.

(Application filed July 15, 1899.)

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UNITED STATES PATENT EETCE.

IRVING R. PRENTISS, OF LYNN, MASSACHUSETTS, ASSIGNOR TO THE GENERALELECTRIC COMPANY, OF NEW YORK.

ELECTRIC-ARC LAM P.

SPECIFICATION forming part of Letters Patent No. 657,450, datedSeptember 4, 1900.

' Application filed J ly 15, 1899. Serial No. 723,893. (No model.)

Ton, whom it may concern:

Be it known that I, IRVING R. PRENTISS, a citizen of the United States,residing at Lynn, in the county of Essex, State of Massachusetts, haveinvented certain new and useful Improvements in Arc-Lamps, (Case No.944,) of which the following is a specification? This invention relatesto arc-lamps. It-s object is to provide a focusing lamp in which the arcis maintained on a substantially-uniform level and to dispense withgearing or wheel-work in its control.

In carrying out the invention I provide a gravity-fed positive electrodeand a negative electrode relatively movable thereto intermittentlycontrolled by a derived-circuit coil which raises it at short intervals,so as to maintain the are at a substantially-uniform level, suitablegripping or detaining devices being provided for supporting the negativeagainst downward displacement when fed toward the arc. By such anorganization each electrode is practically under independent control,the negative being fed from time to time, in accordance with the carbonconsumption, toward a practically-constant arc-level and the positivebeing permitted to gravitate downwardly at a different rate of feed.

Other novel features will be definitely indicated in the claims appendedto this specification.

In the accompanying drawing, which diagrammatically illustrates theinvention, 1 2 represent, respectively, positive and negative electrodesof a focusing arc-lamp, each preferably mounted on an independentcarbonholder 3 4:, to which the electrode is clamped in any suitableway. The are is sprung and its length graduated by means of amagnet-coil 5 in series with the are, said coil controlling an armature,to which is linked one element of the clutch for the carbon-holder. Theparticular type of clutch shown in the drawing is a Brush clutch inwhich two jaws are pivotally connected to a tilting lever 6, linked tothe armature. One of these jaws spans the carbon-holderand the other hasa comparativelysharp edge, which lies parallel with and engages one sideof the carbon-holder. A stop 7, fixed to a stationary part of the lampor lamp-frame, controls the feed intermissions,

.around the arc to regulate the feed.

the clutch being released and permitting the carbons to come intocontact under the influence of gravity when the projection 8 on one ofthe clutch members drops against the stop. The controlling-magnet forthe positive electrode is provided also with a differentially-actingcoil 9 in a derived circuit The negative-carbon holder is fed upwardlyby the derived-circuit coil 9, acting on an armature which controls alifting-clutch 10. A suitable detent fixed to the lamp-frame, which maywith convenience be a clutch similar in construction to that alreadydescribed and which is shown at 11, is provided to hold the .negativecarbon when fed upwardly by the shunt-coil which controls it. Thiscontrolling-coil is preferably an independent coil from that used on thecontrolling-magnet for the positive carbon, but might be the same,though with a less degree of advantage. The active range of thearmatures should be proportioned according to the relative consumptionof the electrodes, so that the amount of upward feed of the negativeshall be just enough to maintain a practically-constant arc-level.

12 is a resistance in circuit with the cutout 13 in a shunt around thelamp, which maintains the integrity of the supply-circuit when the lampis not in operation.

With this construction the operation of the lamp may be-described asfollows: When the current is turned on, the series coil 5 lifts thepositive electrode and strikes the arc, the clutch 6 binding on thecarbon-holder upon an upward movement of the armature. The cut-out 13 issimultaneously opened. As the arc lengthens under the consumption ofcarbon the differential coil 9 weakens the lifting-magnet and shortensthe arc. This action will continue until the controllingarmature movesover a sufficient range to bring the projection 8 into contact with thefixed stop 7, when the clutch releases the carbonholder and the positiveelectrode is fed downwardly under the influence of gravity. When thecurrent through the shunt-circuit reaches a maximum value, the negativecarbon is lifted by the action of the coil 9 and clutch 10, being heldin its raised position by clutch 11., which permits upward movement, butchecks any downward movement. The throw of the armature controlled bythe coil 9 should be adjusted so as to compensate for the consumption ofthe negative carbon and will vary, other things being equal, accordingto the size of the carbon and the amperage of the circuit. Current maybeled into the positive and negative electrodes by brushes engaging thecarbon-holders, as shown at 12 and 13, or in any other convenient way.

It will thus be seen that I provide a focusing arc-lamp in which the arcis maintained on a substantially-uniform level by simple and inexpensivefeeding devices and with out the employment of gearing or wheelwork.

The type of cut-out employed may of course be different from that shownand may provide for closing the circuit around the lamp in case ofaccident to the carbons, as onthe wellknown Brush lamp. As the cut-outforms no part of my invention, I have not deemed it necessary toillustrate in full the various details of practical arc-lamps.

\Vhat I claim as new, and desire to secure by Letters Patent of theUnited States, is-

l. A focusing arc-lamp, comprising relatively-movable positive andnegative electrodes, a series regulating-coil for the positive, ashunt-coil for intermittently lifting the negative, and a clutch fixedto the lamp for supporting the negative when fed up ward.

2. A focusing arc-lamp, comprising relati vely-movable positive andnegative carbons, means for striking the arc, and a shunt-circuitcontrolling an intermittent upward and downward feed of the negative andpositive electrodes, respectively.

3. A focusing arc-lamp, comprising movable positive and negativeelectrodes,the positive being fed by gravity, a clutch controlling saidfeed, a differential coil having windings in series and shunt relationto the arc respectively for controlling the clutch, an independentclutch and a coil in the shunt-circuit for intermittently operating itto raise the negative electrode, and a detent for locking said negativeelectrode in position when raised.

4. A focusing arc-lamp, comprising a gravity clutch-fed electrode, and anegative electrode intermittently raised by a lifting-coil in shunt tothe arc, a detent for holding it in position when raised, the range ofmovement of the shunt-controlled armature being graduated according tothe average rate of consumption of the negative electrode.

In Witness whereof I have hereunto set my hand this 12th day of July,1899.

IRVING R. PRENTISS.

lVitnesses:

BENJAMIN l3. HULL, MABEL E. JACOBSON.

